In order to determine a condition of a driver, for example under the influence of fatigue or alcohol, the reaction time and also the size of the range of vision can be included as important bases for measurement. Reaction time becomes slower when the driver is tired or under the influence of alcohol. In addition, the size of the visual field in which movements are still perceived becomes smaller. This is referred to for example as tunnel vision.
WO 93/16637 discloses a device for acquiring a reflex of a person in which a visual signal is randomly displayed at one of a plurality of predetermined recognizable locations. If the person perceives the signal, the person presses a button. The time between the displaying and the pressing of the button is the reaction time.
WO 01/52722 A1 discloses a method for recognizing the direction of view of a user, in which a light beam is directed into the eye of the user and its reflection is acquired.